1. Field of the Invention
This invention relates to a robotic vacuum cleaner, more particularly to a robotic vacuum cleaner which can proceed with an edge-cleaning mode for improving the cleaning effect.
2. Description of the Related Art
Referring to FIG. 1, a conventional robotic vacuum cleaner 100 is shown to include a casing 11, a plurality of motor-driven wheels 111, a plurality of drive motors (not shown) disposed to drive the wheels 111 so as to move the casing 11 along a floor surface to be cleaned, an electrical control unit 13, and a sensing unit 15. A variety of path programs are stored in the electrical control unit 13 to control the drive motors so as to selectively steer the wheels 111 to cause backward or forward displacement, or rotation of the casing 11. The sensing unit 15 has left and right sensors 151 mounted on lateral front portions of the casing 11, and is electrically connected to the electrical control unit 13 such that once the casing 11 hits an obstacle 91, such as a wall, an article of furniture, and the like, the sensing unit 15 is activated to generate a switching signal to the electrical control unit 13 to enable the electrical control unit 13 to control the wheels 111 to move the casing 11 away from the obstacle 91 for an appropriate distance, and to rotated the casing 11 a random angle before proceeding along the original programmed path.
Although the robotic vacuum cleaner 100 is moved substantially over the entire floor surface to be cleaned, it cannot easily reach edges of the obstacle 91 like corners of the wall or edges of furniture. Therefore, a distance sensor 17 is mounted to a side of the casing 11 such that when the casing 11 is moved away from the obstacle 91 and is rotated, the distance sensor 17 detects a distance between the casing 11 and the obstacle 91. According to the distance detected by the distance sensor 17, the electrical control unit 13 controls the wheels 111 to move the casing 11 along the programmed path, which is spaced from the obstacle 91 by a fixed distance.
However, in operation, it may be necessary to adjust the sensitivity of the distance sensor 17 according to the condition of the environment to be cleaned. While higher sensitivity can achieve a better cleaning effect, it may increase chances of bumping of the casing 11 against the obstacle 91 to result in damage to the robotic vacuum cleaner 100. On the other hand, lower sensitivity results in a larger distance between the casing 11 and the obstacle 91 to thereby reduce the cleaning effect of the robotic vacuum cleaner 100.